Axial plunger pump

ABSTRACT

An improved axial plunger pump construction where the thrust and bending moment produced during the piston operation of the plungers and imposed on the rotating shaft are effectively counteracted by flange means thereby to keep the shaft free of such undesirable forces.

United States Patent Kita Nov. 20, 1973 AXIAL PLUNGER PUMP 2,753,802 7/1956 Omohundro 91 /503 [75] Inventor: Yasuo m y J p 3,236,189 2/1966 Pasker 417/269 [73 1 Assignee: Shimadzu Seisakusho, Ltd., Kyoto,

Japan Primary Examiner-William L. Freeh Assistant Examiner-Ore 0 La Pointe Fld: N .301971 8 7 [22] 0v Att0rneyM0rgan, Finnegan, Durham & Pine [21] Appl. N0.: 203,172

[30] Foreign Application Priority Data Nov. 30, 1970 Japan 106,115 AB TRACT [52] US. Cl. 91/480, 91/503 An improved axial plunger pump construction Wham [51] Int. Cl. F01b 3/02 the thrust and bending moment produced during the [58] Field of Search 91/503, 180; piston operation f th plungers and imposed on the 417/269 rotating shaft are effectively counteracted by flange means thereby to keep the shaft free of such undesir- [56] References Cited able forces UNITED STATES PATENTS 3,498,227 3/1970 Kita 417/269 1 Claim, 1 Drawing Figure AXIAL PLUNGER PUMP BACKGROUND OF THE INVENTION This invention relates to improved axial plunger pumps, more particularly to axial plunger pumps which are operable at a high speed and high pressure.

Axial plunger pumps are known as particularly suited for a high speed and high pressure operation and attempts have been made to provide improved axial plunger pumps for various kinds of use. Generally speaking, however, conventional axial plunger pumps are very complicated in construction and expensive in production cost. The provision of a thrust hearing which has been considered heretofore as indispensable to axial plunger pumps imposes a limitation on the running speed. The operational speed which can be obtained with conventional axial plunger pumps is relatively high but not so extremely high. In addition, the life of thrust bearings which are used is short.

In order to avoid the above drawbacks and to provide an axial plunger pump which is simple in construction and operable at a much higher speed than previously attainable for an extended period of time, a new and improved construction of the axial plunger pump has been proposed as disclosed in US Patent No. .423.227-

Br'iefly stated, the axial plunger pump of the aforementioned US patent includes a housing which forms an enclosed chamber having an inlet and an outlet, and a shaft rotatably mounted within the housing. A cylinder barrel is fixedly disposed within the housing and has an aperture at its center through which the shaft extends. The cylinder barrel also has a plurality of cylinder apertures extending through the barrel parallel to and arranged satellitically with respect to the central apertures. Each of the cylinder aperture is provided with a plunger assembly which comprises a pair of slidable members inserted within the cylinder aperture and spring means disposed between the slidable members. The pair of slidable members are biased away from each other within the aperture by the spring means to form a pump chamber therebetween, the pump chamber being communicated via check valve means with a discharge room outside the cylinder barrel. A pair of end disc means are fixedly mounted to the shaft, one being perpendicular to the axis of the shaft and the other being in an inclined relation to the shaft axis. The two discs are axially spaced away to hold a pair of slidable members in the cylinder apertures between them with the outer end of each slidable member slidably contacting the adjacent disc. A hole is formed in the perpendicular end disc in communication with the inlet of the housing. An axially extending through passage is provided in each slidable member in contact with the perpendicular end disc so that the hole of the rotating perpendicular disc may come into alignment with the passage as the hole in the disc comes into alignment with the axial passage of the slidable member during rotating of the disc, the pump chamber within the cylinder aperture is communicated with the inlet of the housing via the hole and the passage.

In this type of axial plunger pumps, thrust forces produced during pumping operation of the plungers are effectively contained between a pair of discs fixedly mounted on the shaft and, as the result, no thrust bearings are required for supporting the rotating shaft. Absence of thrust bearings enables the axial plunger pump to run' at a speed much higher than possible with the use of a thrust bearing.

Although the axial plunger pumps of the above described type are capable of statisfactory operation, they have a disadvantage in that thrust forces or bending moments are applied to the shaft in the direction somewhat directed toward the shaft axis due to the fact that different reaction forces are created in each of the plungers against the sliding friction between the plunger and corresponding cylinder aperture during extension and retraction strokes of the plungers. The thrust force or bending moment on the shaft imposes undesirable load on the radial bearing used.

Accordingly, the principal object of this invention is to provide axial plunger pumps described having improved means for nullifying thrust acting on the shaft due to the sliding friction between the plunger and the cylinder.

SUMMARY OF INVENTION The axial plunger pump of the type to which this invention is applied comprises a housing forming an enclosed chamber having an inlet and an outlet and a cylinder barrel having an externally disposed annular recess, a central through aperture, a plurality of through apertures satellitically arranged with respect to the central aperture and a port extending from each of the satellitically arranged through apertures to the annular recess. The cylinder barrel is fixedly mounted within the housing and located to provide alignment of the annular recess with the chamber outlet. Rotatably mounted within the housing is a shaft which extends through the central'aperture of the cylinder barrel for axial movement. The cylindrical barrel partitions liquid in the discharge side of the enclosed chamber from the suction side of the chamber. The satellitically arranged apertures in the barrel extend parallel to the central apertures. A pair of discs are fixedly mounted on the driven shaft adjacent the opposite ends of the cylinder barrel. One of the discs is disposed perpendicularly to the axis of the shaft, while the other disc is inclined with respect to the shaft axis. With this arrangement, the distance between the two discs is continuously varied along the circular or circumferential direction of the discs.

An extensible plunger assembly is located in the satellitically arranged apertures in the cylinder barrel and comprises a pair of axially slidable members inserted in the apertures to close the opposite end opening thereof. Spring means is disposed between the slidable members to bias the members away from each other, thereby forming a pump chamber between them within the aperture and also keeping the members in slidable engagement with the adjacent discs. 0f the slidable members, those which are in engagement with the perpendicularly disposed disc are formed with an axially extending through bore.

A check valve means is provided in each of the ports between the satellitically arranged apertures and the external annular recess for selectively communicating the pump chamber with the chamber outlet. Means is also provided for effecting communication between the chamber inlet and the pump chambers in each of the satellitically arranged apertures. This comprises an opening formed in the perpendicular disc in such a position that the opening may come into alignment with the axial bores in the slidable members during rotation of the disc with the shaft.

According to this invention, there is further provided in the slidable members which are in engagement with the perpendicular disc a flange. More specifically, the flange is formed at the end of the slidable members contacting the disc and disposed between the disc and the cylinder barrel in sealing engagement with the disc surface on one hand and in abutting engagement with the end of the cylinder barrel on the other hand.

BRIEF DESCRIPTION OF THE DRAWINGS The FIGURE of the drawing is a side view, partly in cross section of an axial plunger pump embodying the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing there is illustrated an axial plunger pump including a housing or casing generally indicated as 11. The housing 1 1 comprises a pair of end members 11a and 110 and a tubular intermediate member 11b which cooperate together to form an enclosed chamber 12 having an inlet 13 and an outlet 14. The reference numeral 15 indicates a screw means used to connect the three cooperating members 11a, 11b and 110 together and the reference numeral 16 indicates packing seal means disposed between contact surfaces of the cooperating members Ila-11b and llb-l 1c. The member 11a has an end opening 17 for receiving a bearing 18 which in turn rotatably supports a driven shaft 19. The reference numeral 20 indicates an end cover plate having oil seal means 21 for sealingly closing the opening 17 of the member 11a.

The driven shaft 19 which extends into the chamber 12.is connected to a drive mechanism (not shown) on the outside of the housing 11. A pair of discs 22 and 23 are mounted on the driven shaft 19 in a spaced away relation within the enclosed chamber 12. One disc 22 is journalled on the shaft 19 normal to the axis thereof, while the other disc 23 is mounted in an inclined relation with respect to the axis of the shaft so that the distance between the two discs 22 and 24 continuously varies along the circumferential direction thereof. As shown in the drawing, the disc 22 is fitted over the tapered neck portion 19a of the shaft and fixedly connected thereto by a suitable key 24. The disc 23 is also fitted over the inner end of the shaft 19 and is fixedly connected to the shaft by means of a key and a clamping nut 26.

Within the housing 11 there is fixedly mounted a cylinder barrel 27 which is formed with a central aperture 28 having a diameter greater than the outer diameter of the shaft 19. The shaft extends through the central aperture 28 and is rotatably supported by a radial bearing 70 within the central aperture. The radial bearing 70 does not accommodate thrust on the shaft and, accordingly, the shaft may axially slide with respect to the radial bearing. Although, in effect, the axial movement of the shaft is prevented since the thrust and bending moment on the shaft is counteracted at a fixed position as hereinafter described in detail. The cylinder barrel is fixedly secured by screw means (not shown) to the intermediate member 1 lb in a sealing engagement with the use of O-rings 30 so that the outlet 14 is liquidsealed tightly by the cylinder barrel partitioned from the chamber 12. The cylinder barrel 27 is provided at its outer periphery with an annular recess 31 which communicates with the outlet 14. The cylinder barrel 27 is also provided with a plurality of elongated cylindrical apertures 32 arranged in a circle around the shaft 19, in other words, satellitically with respect to the cen tral apertures 28, and extending in directions parallel to the shaft 19.

In each of the cylindrical apertures 32 there is inserted an extensible plunger assembly generally indicated as 40. The extensible plunger assembly 40 comprises a pair of slidable plug members 41 and 42 slidably and fittingly inserted within the cylindrical apertures 32 to close the opposite end openings thereof, respectively, so as to form a pump chamber 44 therebetween in cooperation with the cylindrical apertures 32. A coil spring 43 is disposed between the inner ends of the slidable plug members 41 and 42 to urge the slidable members 41 and 42 away from each other. The outer ends of the slidable members 41 and 42 abut sealingly and slidably on the opposed surfaces 22a and 23a of the disks 22 and 23, respectively. The outer end of the member 41 is in direct contact with the surface 22a while the outer end of the member 32 engages through a swivel block 45 with the surface 23a.

The slidable member 41 is formed with a through passageway 46 for introducing oil into the pump chamber 44 via a window opening 47 formed in the perpendicular disk 22. The window opening 47 is shaped in the form of an elongated arc as shown in the FIGURE so that the passageway 46 may communicate with the chamber 12 only through a certain rotating angle of the disk 22 which corresponds to the extension stroke of the plunger assembly 40. The end surface 48 of the slidable member 41 which is in contact with the inner sur face 22a of the disk 22 is provided with a central cavity 49 and an annular recess 50 so that the oil pressure which will be produced in the pump chamber 44 is supplied between the contact surfaces 48 and 22a so as to provide a static pressure bearing system. In order to provide static pressure bearing system between the swivel block 45 and the surface 23a of the disk 23 as well, the slidable member 42 is provided with an oil passageway 51 extending in its axial direction and communicating with a central port 52 which is formed in the swivel block 45. The swivel block 45 is provided with a central cavity 53 and an annular recess 54 at its end surface 55 which is always in contact with the surface 23a of the inclined disk 23. The port 52 communicates the central cavity 53 with the oil passageway 51.

The pump chamber 44 of each of the cylindrical apertures 32 is communicated to the annular recess 31 through a check valve means 56 which allows the pressure oil to be discharged to the annular recess 31 and then to the outlet 14.

An oil passageway 60 is provided in the end member 11a communicating the inlet port 13 with the enclosed chamber 12. Thus, feed oil supplied to the outlet port 13 may enter the chamber 12 through the passageway 60. From there the oil may flow into the pump chambers 44 via the window openings 47 as the openings 47 in the rotating disc 22 come into alignment with the axial passageways 46.

According to the important aspect of this invention,

each of the slidable members 41 inserted within the cylindrical apertures 32 is integrally formed with an outer flange 41a which is of a greater diameter then the apertures. With the slidable members 41 in position within the apertures, the outer flanges 41a thereof are held between the perpendicular disc 22 and the fixed cylinder barrel 27. As noted above, the outer end surfaces 48 of the flanges 41a are kept in constant sealing engagement with the surface 22a of the disc 22 due to the fact that the slidable members 41 are axially biased toward the disc 22 by the force of the spring members 32. It should be noted that, for the purpose hereinafter explained in detail, an annular shoulders 41a of the flanges 41a must be kept in abutting engagement with the fixed cylinder barrel 27. Accordingly, the flanges 41a are so formed that the axial length thereof between the outer end surface 48 and the annular shoulder 41b may be greater than or, at least, substantially the same with the axial gap between the contact surface 22a of the disc 22 and the opposing end surface of the fixed cylinder barrel 27.

The operation of the apparatus illustrated in FIG. 1 is as follows:

When the shaft 19 is driven to rotate, the two discs 22 and 23 are rotated with the outer ends of the slidable members 41 and the swivel blocks 45 engaging with the slidable members 42 sliding on the opposed surfaces 22a and 23a of the discs 22 and 23, respectively, under pressure and sealing condition. The distance between the two diescs 22 and 23 at the position of each of the plunger assemblies 40 varies continuously. While the slidable member 41 abuts against the disc 22 perpendicular to the axis of the shaft, there is no substantial movement of the member 41, the other slidable member 42 abutting against the inclined disc is imparted a reciprocating movement along the cylindrical aperture 32 whereby the volume of the pump chamber 44 is varied. In the extension stroke of the plunger assembly 40, oil flowing into the chamber 12 from the inlet 13 and passing through the passageways 60 is introduced to the pump chamber 44 through the window opening 47 of the disc 22 and the passageway 46 of the member 32, while the check valve 56 is in a closed position. This is the suction stroke; During the retraction stroke of the plunger means 40, pressure oil is discharged through the check valve 56 to the annular recess 31 which is communicated with the outlet 14, while the slidable member 41 travels the blind portion of the disc 22 so that the passageway 46 is kept in a closed condition.

Since the reciprocating movement of the plunger assemblies 40 during the fluid pumping operation is effected between the pair of discs 22 and 23 both being fixedly mounted on the shaft 19, the thrust due to the pumping operation of the plunger assemblies is fully supported by the discs 22 and 23 and, therefore, is prevented from acting directly on the shaft. This, in turn, enables the shaft 19 to be supported by radial bearings 22 and 23 using no thrust bearings.

However, during reciprocating pumping movement,

each of the slidable members 42 is acted on reaction forces due to sliding friction between each of the members 42 and the corresponding cylinder 32. The reaction forces, in turn, act through the inclined disc 23 on the shaft 19 to impart thrust force thereto. In order to achieve a simple as well as durable construction of the plunger pump, the above-mentioned thrust acting on the shaft must effectively be counteracted or otherwise be nullified. According to this invention, the flange portions 41a integrally formed on the slidable members 41 carry out the desired function. As explained hereinabove, the flanges 41a of the slidable members 41 are disposed between the fixed cylinder barrel 27 and the perpendicular disc 22 in abutting engagement with these component parts. With the disc 22 being fixedly mounted on the shaft 19, the thrust on the shaft due to the above cause is transmitted via the fixed disc 22 to the flanges 41a. The flanges 41a in turn carry it to the cylinder barrel 27. The cylinder barrel being fixedly mounted to the housing 11, it receives and counteracts the thrust force transmitted to the flanges 41a thereby nullifying it. In this manner, any thrust force acting on the shaft due the frictional engagement between the slidable members 42 and the cylinder 32 is effectively negated in the disc 22 by the counteraction of the fixed cylinder barrel 27 via the flanges 41a of the slidable members 41.

As the result, a stable and smooth high speed operation of the axial plunger pump is assured.

What I claim is:

1. In an axial plunger pump comprising:

a housing forming an enclosed chamber having an inlet and an outlet;

a cylinder barrel having an externally disposed annular recess, a central through aperture, a plurality of through apertures satellitically arranged with respect to the central aperture, a port extending from each of the satellitically arranged through apertures to the annular recess;

a driven shaft rotatably mounted within the enclosed chamber and extending through the central aperture of the cylinder barrel;

a pair of discs fixedly mounted on the driven shaft adjacent the opposite ends of the cylinder barrel, one of said discs being disposed perpendicularly to the driven shaft, the other of said discs being inclined with respect to the axis of the shaft;

a plurality of plunger assemblies located in the satellitically arranged apertures in the cylindrical barrel, each of said plunger assemblies comprising a pair of slidably arranged members and a spring located between the members to bias the members away from each other to form a pump chamber within the aperture and to keep the members in slidable engagement with the adjacent discs, each of said slidably arranged members in engagement with the perpendicular disc having an axial through bore;

a check valve in each of the ports between the satellitically arranged apertures and the external annular recess for communicating the pump chamber with the chamber outlet; and

means for effecting communication between the chamber inlet and the pump chambers in each of the satellitically arranged apertures comprising an opening so formed in the perpendicular disc as to come into alignment with the axial bores in the plungers during rotation of the disc with the shaft, wherein the improvement comprises said cylinder barrel being fixedly mounted within the housing and located to provide alignment of the annular recess with the chamber outlet, said rotatably mounted driven shaft being mounted to afford axial sliding thereof and a flange on each of the slidably arranged members which are in engagement with the perpendicular disc which flange is in both sealing contact with the disc and abutting engagement with the end of the fixed cylinder barrel. 

1. In an axial plunger pump comprising: a housing forming an enclosed chamber having an inlet and an outlet; a cylinder barrel having an externally disposed annular recess, a central through aperture, a plurality of through apertures satellitically arranged with respect to the central aperture, a port extending from each of the satellitically arranged through apertures to the annular recess; a driven shaft rotatably mounted within the enclosed chamber and extending through the central aperture of the cylinder barrel; a pair of discs fixedly mounted on the driven shaft adjacent the opposite ends of the cylinder barrel, one of said discs being disposed perpendicularly to the driven shaft, the other of said discs being inclined with respect to the axis of the shaft; a plurality of plunger assemblies located in the satellitically arranged apertures in the cylindrical barrel, each of said plunger assemblies comprising a pair of slidably arranged members and a spring located between the members to bias the members away from each other to form a pump chamber within the aperture and to keep the memBers in slidable engagement with the adjacent discs, each of said slidably arranged members in engagement with the perpendicular disc having an axial through bore; a check valve in each of the ports between the satellitically arranged apertures and the external annular recess for communicating the pump chamber with the chamber outlet; and means for effecting communication between the chamber inlet and the pump chambers in each of the satellitically arranged apertures comprising an opening so formed in the perpendicular disc as to come into alignment with the axial bores in the plungers during rotation of the disc with the shaft, wherein the improvement comprises said cylinder barrel being fixedly mounted within the housing and located to provide alignment of the annular recess with the chamber outlet, said rotatably mounted driven shaft being mounted to afford axial sliding thereof and a flange on each of the slidably arranged members which are in engagement with the perpendicular disc which flange is in both sealing contact with the disc and abutting engagement with the end of the fixed cylinder barrel. 